from collections import deque
#单线程队列，也是双端队列
q = deque(maxlen=2)
print(len(q)==None)
while len(q):
    print("1")
# q.append(1)
# q.append(2)
# print(q)
# q.append(3)
# print(list(q))
# print(q.popleft())
